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Abstract
Drought on the Canadian prairies is the single most limiting factor to crop yield. Several indices have been developed that indicate the onset, severity, and persistence of drought. This study was conducted to assess the validity of the Palmer Drought index for characterizing drought on the Canadian prairies. When the empirical relationship used by Palmer for calculating the weighting factor K was applied to historical weather data, the relationship appeared inappropriate. There was only a weak relationship between K and the moisture balance variables from which it is usually calculated. The regional correction factor was calculated to be 14.2, which is lower than the generally accepted value of 17.67. A soil water model, the Versatile Soil Moisture Budget (VMB), was coupled with the Palmer model to improve the modeling of soil water. The drought index obtained with the VMB explained 49% of the variation in wheat yield, while the original Palmer index explained 33%. In addition, a new drought index, which does not rely on the weighting factor K explained 57% of the variation in wheat yield, which is almost twice the variation explained by the original Palmer index.
Abstract
Drought on the Canadian prairies is the single most limiting factor to crop yield. Several indices have been developed that indicate the onset, severity, and persistence of drought. This study was conducted to assess the validity of the Palmer Drought index for characterizing drought on the Canadian prairies. When the empirical relationship used by Palmer for calculating the weighting factor K was applied to historical weather data, the relationship appeared inappropriate. There was only a weak relationship between K and the moisture balance variables from which it is usually calculated. The regional correction factor was calculated to be 14.2, which is lower than the generally accepted value of 17.67. A soil water model, the Versatile Soil Moisture Budget (VMB), was coupled with the Palmer model to improve the modeling of soil water. The drought index obtained with the VMB explained 49% of the variation in wheat yield, while the original Palmer index explained 33%. In addition, a new drought index, which does not rely on the weighting factor K explained 57% of the variation in wheat yield, which is almost twice the variation explained by the original Palmer index.
Abstract
The Canadian prairies are a major producer of grain, much of which is produced under rain-fed agriculture. The amount and timing of precipitation are critical to grain production. Information on the precipitation trend is therefore vital to this region. Regression analysis was used to establish linear trends of precipitation amounts, number of precipitation events, and variance of precipitation at 37 stations with 75 yr of record across the Canadian prairies. The precipitation was further split into rainfall and snowfall, and similar analysis was performed on these variables. The analysis showed that there has been a significant increase in the number of precipitation events mainly due to an increase in the number of low-intensity events. As such, precipitation events are not getting more intense on the Canadian prairies. The number of precipitation events (excluding events that are 0.5 mm or less) has increased by 16 events during the last 75 yr. Precipitation and rainfall amounts have increased significantly by 0.62 and 0.60 mm yr−1, respectively, on the Canadian prairies during the last 75 yr. During the period from 1921 to 1960 the trends in precipitation, rainfall, and snowfall were not statistically different from zero. However, from 1961 to 1995, snowfall has declined significantly by 0.95 mm yr−1. The trends in the most recent period (1961–95) were also significantly different from those in the 1921–60 period for snowfall. The difference in trends between the two periods for snowfall, combined with the inverse relationship in the rainfall–snowfall trends, suggest that these trends may be related to climate change.
Abstract
The Canadian prairies are a major producer of grain, much of which is produced under rain-fed agriculture. The amount and timing of precipitation are critical to grain production. Information on the precipitation trend is therefore vital to this region. Regression analysis was used to establish linear trends of precipitation amounts, number of precipitation events, and variance of precipitation at 37 stations with 75 yr of record across the Canadian prairies. The precipitation was further split into rainfall and snowfall, and similar analysis was performed on these variables. The analysis showed that there has been a significant increase in the number of precipitation events mainly due to an increase in the number of low-intensity events. As such, precipitation events are not getting more intense on the Canadian prairies. The number of precipitation events (excluding events that are 0.5 mm or less) has increased by 16 events during the last 75 yr. Precipitation and rainfall amounts have increased significantly by 0.62 and 0.60 mm yr−1, respectively, on the Canadian prairies during the last 75 yr. During the period from 1921 to 1960 the trends in precipitation, rainfall, and snowfall were not statistically different from zero. However, from 1961 to 1995, snowfall has declined significantly by 0.95 mm yr−1. The trends in the most recent period (1961–95) were also significantly different from those in the 1921–60 period for snowfall. The difference in trends between the two periods for snowfall, combined with the inverse relationship in the rainfall–snowfall trends, suggest that these trends may be related to climate change.
